Re: Linear Path Shooter vs. Circular Path Shooter?
 

It translates into approx 21 mph, assuming no slipping.

3600 rpm / 60 min/sec = 60 rev/sec

60 rev/sec * pi*4/12 ft/rev = 62.8 ft/sec

62.8 ft/sec / 2 = 31.4 ft/sec

31.4 ft/sec * 3600 sec/hour / 5280 ft/mile = 21.4 mph

Re: Linear Path Shooter vs. Circular Path Shooter?
 

In Lunacy we ran timing belts instead of wheels in our shooter, in an attempt to compensate for the holes in the orbit balls. The belts were driven with only a small gear reduction from a CIM motor, and we never, at any point in the season, had an issue with them. They never came off, never wandered, no issues at all. A lot of design and work went into building a stable, adjustable system that would allow us to ensure everything was perfectly parallel, and using belts with teeth in them also helped.

I'm not saying I recommend going this path, but it certainly is possible to get your belts up to speed and keep them there without any issues.

Re: Linear Path Shooter vs. Circular Path Shooter?
 

Ether. That 31.4 ft/sec sounds like it might do the job. I wonder what a CIM motor at full speed with a direct drive 6 inch wheel would be? Just don't have the CIM specs handy.

Re: Linear Path Shooter vs. Circular Path Shooter?
 

A circular shooter gives the Frisbee spin and more accuracy

Re: Linear Path Shooter vs. Circular Path Shooter?
 

It can be argued that 1 circular shooter may use less space than 2 parallel shooters, if you are trying to minimize the length of the shooter, and width doesn't matter.

Re: Linear Path Shooter vs. Circular Path Shooter?
 

CIM free speed is 5310 rpm. But you don't want to drive your shooter wheel at free speed. You need some headroom to accelerate back to the setpoint after a frisbee passes through.

Re: Linear Path Shooter vs. Circular Path Shooter?
 

so does a linear shooter

What is your source for this statement?

Re: Linear Path Shooter vs. Circular Path Shooter?
 

You can see from some of our testing video (Thanks Kevin!) that we have tried a couple of different approaches. Granted, some of the tests aren't as valid because the mechanical setup's were a bit shoddy.
When you get to the 90 deg. circular shooter, you can notice some issues with the stability of the wall. We will be working on that tonight.
One really important take away from this testing is that increased RPM of the shooing wheel did not always translate to further distance. This is because the slipping that is occurring between the wheel and the Frisbee. Again, this is something we will be addressing tonight.

BTW, High Speed Video Capture (HSVC) is rapidly becoming one of our favorite new prototyping tools.

This is in Std. Res.
http://www.youtube.com/watch?v=p5bLi...ature=youtu.be

This one is in 1080.
http://www.youtube.com/watch?v=Wa6pc...ature=youtu.be

Re: Linear Path Shooter vs. Circular Path Shooter?
 

Some of the confusion/disagreement/misunderstanding/whatever seems to be because folks are unintentionally discussing different implementations of the linear shooter. The major sub-categories would seem to be "single drive side" vs. "double side drive" and "nip point contact" vs. "continuous contact". So far I've mostly seen videos of "single side drive, nip point contact". I haven't seen any videos of teams prototyping a "single drive side, continuous contact" design...yet.

Re: Linear Path Shooter vs. Circular Path Shooter?
 

Why not just quickly test both? You're going to have some discrepancies between the performance of the two anyway. Also, you might be using different materials than other teams and the such. Grab a bunch of wheels and have at it. You guys might also develop another idea just from doing that!

Good luck!

Re: Linear Path Shooter vs. Circular Path Shooter?
 

I stand corrected on the belting. I misunderstood what was meant by belting; I was imagining that the belting in question was polycord or some other cord variant.

"NIP point contact"? Can you elaborate on to what this means?

Re: Linear Path Shooter vs. Circular Path Shooter?
 

This depends largely on wheel diameter. If you can achieve the linear velocity and contact time you're seeking using wheel diameter < the disc, even a dual linear can be shorter (final shot axis) than a 90deg turn.

Re: Linear Path Shooter vs. Circular Path Shooter?
 

One consideration for the circular vs linear shooter is how the Frisbee is released. The circular shooters I've seen in videos have a very gentle release, the outer wall very gradually moves away from the wheel until the gap is larger than the Frisbee. This means that small variations in Frisbee geometry, perhaps from prior rough handling, give slightly different release points. The theory seems to be that the Frisbee is "up to speed" well before the release point and so the exact point where it loses wheel contact doesn't matter.

The linear shooter used by the robotin3days folks uses a compliant wheel to hit the Frisbee with a pulse of energy. Given the speed involved, it it a very quick, violent, pulse. Ignoring the risk of Frisbee damage, there is no way to do that without adding some flex to the Frisbee and corresponding random velocity. I'm not at all worried that belts can't take the speed or forces required, just Google "serpentine belt" and see how they are used in cars.

Replacing the two wheels with two wheels connected by a belt, or 5 wheels and a belt if you want to go all-tank style, could mean you don't have to pinch the Frisbee as hard because you have more distance (= time) to add energy to it. It sounds like this could be better, but convincing experimental measurement of the magnitude of the effect is what we're lacking in this discussion.

Re: Linear Path Shooter vs. Circular Path Shooter?
 

My understanding of this is that he means the very short contact time and small contact area that a wheel and a linear wall creates compared to a curved wall and a wheel.

Re: Linear Path Shooter vs. Circular Path Shooter?
 

When making prototypes, keep in mind there are more variables than just linear versus curved.

Our linear prototype currently worked AWESOME, and our curved is merely pretty darn good.

We're smart enough to realize we haven't proved anything yet, and need to explore more.